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Geology

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Jan 9, 2024

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/ ANALYZING DATA Topography Mass deficiencies are observed under mountains because the crustal roots that underpin them have low densities relative to the surrounding mantle. Thus there is a buoyant force that keeps the visible portion of a mountain above the Earth surface in isostatic equilibrium, isostasy , with the area beneath the surface - the root. The buoyant force is upward and equal in magnitude to the weight of the displaced mantle. Topography is therefore attributable to the variable densities of the materials that comprise Earth. These measurements of crustal thickness were obtained using the seismic waves from distant earthquakes that pass up through the crust and are recorded on seismometers. These seismometers are usually located in towns that are in valleys between the tall mountains . Elevation Crustal Thickness 4km 68 km 3.8 km 65 km 1.8 km 50 km 0.3 km 40km Source: Beck, S.L. et. al. Crustal thickness variations in the central Andes (1996) Geolog11 24(2'' 407-410. . 1 ' 1• Elevation Crustal Thickness 4.9 km 86 km 3.6km 72 km 2.5km 58 km 0.2 km 38 km Source: Gilligan, A. ~t al. The Crustal Structure of the Western Himalayas and Tibet (2015)) Journal of Geophysical Research, Solid Earth, 24 April · Flin S . . . Copyright© 2022 Flinn Scientific, Inc . All Rights Reserved n c1ent1fic and its affiliates are not res onsible f . . . P or any modrficat1ons made by end users to the content posted in its original format. I} YI I
CLASS ___ _ DATE ___ _ NAME ____________ _ j Rdcky Mountains . :i ' crustal Thickness Elevation 40km 2km I 2.8km 45km 0.5km 25 km 1.5 km 30km Source: Schmandt, B. et. al. Distinct crustal isostasy trends east and west of the Rocky Mountain Front (2015). Geophys. Res. Lett., 42, 10290-10298. 1. SEP Identify Patterns What general relationship between elevation and crustal thickness do you observe? ~J~~~V'I \V\C~ \-¥\'l.- Of'vt~l \.ht.cti V'U cl~-ts Q.$$~\l. L 2. SEP Analyze Data The continental crust that forms mountains and their roots sits on top of the mantle. Which of the two materials has the higher density? Explain. Th-e. w- eJ.. (),.__ C\. V\') hr , "-i..\; 1 \ -t c <A.,~ 't +Yl't c '/\A-<.~ " r--Vl,. "'- \.-0. 1 u.-\- {. \Q VV'lci v'l J.. "e_ \/) l~ ho~ flt \ Nl J l/lv'trA lN "' \'( \ti t '{t' q ~s {A ~r c)l'f\ -s \ \-.y . Copyright© 2022 Flinn Scientific, Inc. All Rights Reserved . Flinn Scientific and its affiliates are not responsible for any modifications made by end users to the content posted in its original format.
\ NA ME DATE ---- CLASS 3. SEP Enga . --- hi h ge •n Argument Would g mountain to be stron you expect the gravitational force near a very ger or weaker than predicted. Explain. :I"~ w~u.l el be W...t\. "-t, .... 1 ,t-- ..\- ¼ ., J'I-\ VL c-.. rJ.,. q s ") ~t \.v,-1 fcf I \- J_ \d V'' I,. n{, h -\.- C. I I °' r-.d-. -5 ni» ,, \j\Q,vi a f' V) t- dd, WV) • 4 · SEP Use Math Suppose that a mountain rises 2.0 km above the surrounding land and that it is isostatically supported by a deep crustal root that extends into the mantle. If the continental crust that forms the mountains and its root has a density of 2800 kg/m 3 and the mantle replaced by the root has a density of 3300 kg/m 3 , find the depth of the root below the normal depth of the crust. Note that the area of the mountain and its root do not affect the answer , but that you will need to use the difference in densities to find the depth of the root. "2'500 · 1 Oo o s. SEP Construct an Explanation What do you think accounts for deviations from the general relationship the data indicate about elevation versus crustal thickness? Explain. ~y c ~~I J c0- \Aeci y CAbt1of'vY'a I ,'-l-~, SiJ.Ch ,/l fi: tAl I b ~~ ) ~ vs > w~ i-\.e, ~ ) t' · C1._~ "{\(i\V' 0\ J& vJ \;\ l\t lr, vi 0- \)\J [ t 0. V\ v e_5[1.-lf ~v\{J Vl - . S • tifi Inc All Rights Reserved . Copyright © 2022 Fltnn cien c, · t t posted in its original format. . d.fi tions made by end users to the con en Flinn Scientific and its affiliates are not responsible for any mo I ca
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N AME DATE ---- CLASS --- 6. SEP Construct an Ex . denser su planatlon What does th · to erode a~:rting matter indicate about their /if: idea that mountains "float' on to their own? y :~n . they would if they simply sat :ans~ Should they take longer l '. . P am. n su aces with densities equal \\.-- t h t I VI () Jc D\ t-t ~ -1-\Q. \ ~-t s e V\ \~ ( ~'V" l9 Y) (}Q,V' )U sv- Q~t +' 'i Y"'-" ~w rJ.iot t" ~\ s-1-N~ef ow>. fl\ Of'l ~v-r~IJI{, 1 \-- 11.ld ¥:A VL-t ( 11. ~v-- "' 1)mf'-,li-. (}Mt VI (}. \J\ d'- ~-ro Je " F lin n S cie n tifi c a . Cop yri ght © 20 . nd tt s affil i ates are not r espons i ble f 22 Flinn Scie n tific, In c. Al l Rig h ts Re or any mod i ficati served . ons mad e by end use rs to the content posted in its o . . . ng,nal formal